1,3-Butadiene (sometimes referred to herein as “butadiene”) is an important monomer for the production of synthetic rubbers including styrene-butadiene-rubber (SBR), polybutadiene (PB), styrene-butadiene latex (SBL), acrylonitrile-butadiene-styrene resins (ABS), nitrile rubber, and adiponitrile. Adiponitrile is used in the manufacture of Nylon-66 (White, Chemico-Biological Interactions, 2007, 166, 10-14).
Butadiene is typically produced as a co-product from the steam cracking process, distilled to a crude butadiene stream, and purified via extractive distillation (White, Chemico-Biological Interactions, 2007, 166, 10-14).
On-purpose butadiene has been prepared among other methods by dehydrogenation of n-butane and n-butene (Houdry process); and oxidative dehydrogenation of n-butene (Oxo-D or O-X-D process) (White, Chemico-Biological Interactions, 2007, 166, 10-14).
Industrially, 95% of global butadiene production is undertaken via the steam cracking process using petrochemical-based feedstocks such as naphtha. Production of on-purpose butadiene is not significant, given the high cost of production and low process yield (White, Chemico-Biological Interactions, 2007, 166, 10-14).
Given reliance on petrochemical feedstocks and, for on-purpose butadiene, energy intensive catalytic steps; biotechnology offers an alternative approach via biocatalysis. Biocatalysis is the use of biological catalysts, such as enzymes, to perform biochemical transformations of organic compounds.
Accordingly, against this background, it is clear that there is a need for sustainable methods for producing intermediates, in particular butadiene, wherein the methods are biocatalyst based (Jang et al., Biotechnology & Bioengineering, 2012, 109(10), 2437-2459).
Both bioderived feedstocks and petrochemical feedstocks are viable starting materials for the biocatalysis processes.
The generation of two vinyl groups into medium carbon chain length enzyme substrates is a key consideration in synthesizing butadiene via biocatalysis processes.
There are no known enzyme pathways leading to the synthesis of butadiene in prokaryotes or eukaryotes. Three potential pathways have been suggested for producing 1,3-butadiene from biomass-sugar: (1) from acetyl-CoA via crotonyl-CoA; (2) from erythrose-4-phosphate; and (3) via a condensation reaction with malonyl-CoA and acetyl-CoA. However, no information using these strategies has been reported (Jang et al., Biotechnology & Bioengineering, 2012, 109(10), 2437-2459).